Malignant tachyarrhythmia, for example, ventricular fibrillation, is an uncoordinated contraction of the cardiac muscle of the ventricles in the heart, and is the most commonly identified arrhythmia in cardiac arrest patients. If this arrhythmia continues for more than a few seconds, it may result in cardiogenic shock and cessation of effective blood circulation. As a consequence, sudden cardiac death (SCD) may result in a matter of minutes.
In patients at high risk of ventricular fibrillation, the use of an implantable cardioverter defibrillator (ICD) system has been shown to be beneficial at preventing SCD. An ICD system includes an ICD, which is a small battery powered electrical shock device, may include an electrical housing, or can electrode, that is coupled to one or more electrical lead wires placed within the heart. If an arrhythmia is sensed, the ICD may send a pulse via the electrical lead wires to shock the heart and restore its normal rhythm. Owing to the inherent surgical risks in attaching and replacing electrical leads directly within or on the heart, methods have been devised to achieve a similar effect to that of a transvenous ICD system connected directly to the heart without placing electrical lead wires within the heart or attaching electrical wires directly to the heart.
Extravascular medical leads and systems, for example, subcutaneous implantable cardioverter-defibrillator (SubQ ICD) systems, have been devised to deliver electrical impulses to the heart by the use of a defibrillation lead placed subcutaneously above the ribcage and/or sternum of the patient. However, when gaining subcutaneous or substernal access to the torso for insertion of medical leads or other medical devices, it is beneficial to have tools specifically suited to accessing the anatomical space to achieve repeatable, atraumatic access. Indeed, in the absence of appropriate tools, physicians may use their fingers or forceps for blunt dissection to access the necessary anatomy, which can cause wounds, tissue damage or affect overall healing time.